Aussie scientists' time travel breakthrough

Rose Powell

FLUX CAPACITOR: Australian scientists use light particles to simulate a key process that shows time travel may be possible.

A group at University of Queensland physicists have used light particles to simulate a key process that indicates how time travel might be possible despite well-known clashing theories.

Led by PhD student Martin Ringbauer, the research will add to the study of how time travel could be possible and how core scientific theory quantum mechanics might change in new environments.

The team was able simulate single particles of light, known as photons, travelling along a path in space-time that returns the travelling object to the same point at an earlier time, known as a closed timelike curve.

"This research is certainly not a demonstration of time travel or proof it's possible. We were starting from the point to discover what would happen if it was possible," Ringbauer told Fairfax Media.

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Ringbauer says the intriguing issue at the heart of this research was not the science-fiction potential but the insights time travel might give in the incompatible relationship between successful scientific theories: Einstein’s general relativity, and quantum mechanics.

While time travel is possible in Einstein's theory of general relativity with closed timelike curves, it seems to cause several deal-breaking paradoxes in the real world.

One such issue that even the unscientific can understand is the "grandfather paradox", in which the person embarking upon a time travel mission could prevent their grandparents from meeting, blocking their eventual birth and therefore the opportunity to ever take the trip.

“Quantum systems can exist in a mixture of existing and non-existing states. In the classical state, you can either exist or not, but quantum systems can operte in both which resolves the paradoxes and time-travel can be formulated in a self-consitent way," Ringbauer said.

Unfortunately for those mulling over which key historical moment they're keen to hit up first, the classical state is physical objects, such as humans.

"We've not made any comment about the macroscopic case, which presents many paradoxes which makes it implausible."

Another issue for aspiring century skippers is the existence of closed timelike curves, which are possible but as yet only in theory with extreme gravitational effects such as blackholes which could skew the quantum physics rules.

The study has been published in academic journal Nature. The scientists involved were Matthew A Broome, Casey R Myers, Andrew G White and Tim C Ralph.

University of Queensland physics professor Tim Ralph told The Spectator the study provides insights in to where and how nature may behave differently from how current theories predict.

“The properties of quantum particles are ‘fuzzy’ or uncertain to start with, so this gives them enough wiggle room to avoid inconsistent time travel situations,” he said, adding there were situations where standard quantum rules did not apply, such as near black holes.

The team was able simulate single particles of light, known as photons, travelling along a path in space-time that returns the travelling object to the same point at an earlier time, known as a closed timelike curve.

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